3 hours and I'm amazed that nobody has made the requisite the "don't use cable management arms they ruin airflow" comment. For what it's worth I don't always believe that's the case; or the trade-offs are worth it.
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Mark Henderson♦Aug 3 '12 at 21:14

1

all of the servers i use have intelligent cooling systems. even with the cable management arms, nearly all of the servers in my data center run at the lowest fan speeds. only the heavily CPU bound workloads demand boosted fans speeds, and they are still not at max speed. oh, did i mention that i use cable management arms extensively? i even use them to deal with excess power cord.
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longneckAug 4 '12 at 1:30

@Mark, it depends to some extent on the arm. Servers designed to be rack mounted and supplied with their own arm are normally designed with the arm's interference to the airflow taken into account.
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John GardeniersAug 4 '12 at 3:44

4 Answers
4

Even in the case of unshielded cables and "dirty" power, I've yet to see it cause a problem. The interference generated by the power cables is small enough that it doesn't interfere with the digital networking singles going across your RJ45 cables, especially over such a short distance in the cable management arm. And I've seen 4 power cables, 6 CAT5 cables and a half dozen cables for miscellaneous peripherals (SCSI, USB, serial, etc) all twisted together into one long mess without issues.

Analog may be another story, but as long as it's digital, you're safe, whether the cables are shielded or not.

The only places I've seen where you have worry about interference from power source in networking cables are near really big power sources (like you'd find in a 5-ton AC unit, for example) or when running cables over the 100 meter standard "limit" for CAT-5.

I am by no means an expert but I was always taught that as long as you were using shielded category cable you can run them side by side. We did this for multiple servers in a full 42U rack without any issue. However we also had PDUs to make sure we were sending clean power in the first place.

FWIW, I havent seen many people using shielded BaseT in years...
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Mike PenningtonAug 3 '12 at 21:46

your cat5/6 cable is shielded? i challenge you to sacrifice one of the network cables in your server rack to a pair of scissors. i would bet that there is no shielding in there at all.
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longneckAug 4 '12 at 1:28

@longneck, I'm with you, but no scissors are required... if it's shielded, the braid must be terminated into a metallic RJ45 jack
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Mike PenningtonAug 4 '12 at 4:18

i usually zip-tie the power to the bottom because once the power is in, it's almost never moved. for everything else i use velcro ties to keep the cables at the top of the arm. i do this more for convenience than separation, but it does give you separation, too!

If possible I'd tie the power cables to the bottom of the arm and the network cables to the top. Even an inch of separation would be positive. As mentioned above the lengths involved probably won't lead to many issues, but it could exacerbate issues with very long runs (i.e. through an IDF / MDF to centralized switches) or if there's interest in 10GE, which is notoriously fickle even with STP.